Star Light, Star Bright

The night sky is bursting with stars when viewed through a telescope. But even with a telescope, stars are too far away for us to learn what they are made of just by viewing them. So how can scientists learn about the composition of stars?

The Back Story

Stars give off light in the electromagnetic spectrum. The spectrum of light from a given star looks different depending on the elements that make up the star.

Credit: NASA Goddard Space Flight Center

Source: http://www.flickr.com/photos/gsfc/6883342722/

License: CC BY-NC 3.0

Galaxies are composed of billions of stars and give off a wide spectrum of light
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Stars aren’t the only objects that give off light. Anything that glows gives off light, including solids that have been heated to extremely high temperatures, flames, and very hot gases.

A scientific measuring device called a spectrograph can analyze the light from stars or other glowing objects. It breaks down the light into its different wavelengths. The spectrum of light revealed by a spectrograph can be used to determine the elements that a glowing object contains.

Can You Apply It?

A simple glass prism can be used to break light into different wavelengths, producing a rainbow of colors of light. The earliest spectrographs used a lens to focus light and a prism to separate it into individual wavelengths. Later spectrographs replaced the prism with another device. What is it, and how does it work? What advantage does this device have over a simple prism?

Each star or other glowing object has a characteristic spectrum with dark lines in it. What do the dark lines represent? Why do they form?

What are some elements that are common in the atmosphere of stars?

Helium is a very useful element. It is used to fill blimps, weather balloons, and party balloons, among many other uses. Because helium is so light, it isn’t held in Earth’s atmosphere by gravity. Instead, it drifts off into space. If there is no naturally occurring helium on Earth, how was helium discovered?

Besides learning about the composition of stars, spectrographs can be used to learn about matter here on Earth. What else can be learned from spectrographs? What discoveries have been made with them?